Excessive exposure to fluoride causes a defect of the tooth enamel known as dental fluorosis. In its most severe form, dental fluorosis is a seriously disfiguring condition, marked by brown and black staining of the teeth, often with extensive pitting, chipping, and crumbling of the enamel. Based on the most recent national estimates, about 1% of the adolescent population in the United States currently has severe dental fluorosis. (CDC 2010). Children with medical conditions that induce polydipsia (excessive thirst) are at particular risk of developing severe fluorosis. As noted in the Annals of Internal Medicine:

“Prolonged polydipsia (excessive thirst) may be hazardous to persons who live in areas where the levels of fluoride in drinking water are not those usually associated with significant fluorosis.”
SOURCE: Sauerbrunn BJ, et al. (1965). Chronic fluoride intoxication with fluorotic radiculomyelopathy. Annals of Internal Medicine 63: 1074-1078.

Diabetes insipidus is one such medical condition that produces polydipsa. In the following three studies, scientists documented the occurrence of severe fluorosis among children with diabetes insipidus. While proponents of water fluoridation state that the program is entirely “safe,” the children in these studies were living in communities with “optimally” fluoridated water.

Studies Finding Severe Fluorosis Among Children with Diabetes Insipidus

“Hereditary diabetes insipidus is a rare endocrine disorder caused by a deficiency of the antidiuretic hormone, vasopressin. The disease is characterized by polyuria, extreme thirst, and polydipsia. In this study of six affected members from two families with hereditary diabetes insipidus, it was found that two children who drank water fluoridated at optimum levels developed moderate to severe fluorosis. By contrast, four other affected patients who did not consume fluoridated water showed normal dentitions. This report indicates that dental fluorosis may be an important complication of diabetes insipidus, and demonstrates the possibility that excessive consumption of optimally fluoridated water can lead to severe developmental enamel defects.”
SOURCE: Seow WK, Thomsett MJ. (1994). Dental fluorosis as a complication of hereditary diabetes insipidus: studies of six affected patients. Pediatr Dent. 16(2):128-32.

“Extremely heavy intake of water with a fluoride content of about 0.5 ppm during the early years of tooth development has produced severe to mild fluorosis of the teeth in the family members affected by hereditary pituitary diabetes insipidus.”
SOURCE: Klein H. (1975). Dental fluorosis associated with hereditary diabetes insipidus. Oral Surg Oral Med Oral Pathol. 40(6):736-41.

“Children with polydipsia as in nephrogenic diabetes insipidus consume excessive quantities of water. We are reporting two children with nephrogenic diabetes insipidus and fluorosis, and suggest looking for evidence of fluoride toxicity in individuals with polydipsia. . . . Our patients’ daily fluid consumption while hospitalized and at home ranged from 2 1/2 to 6 times normal daily intake. They have lived in communities where the fluoride concentration is 1 ppm, the recommended amount to control caries and prevent fluorosis in children with average daily water intake. However, the patients’ excessive ingestion of water has increased the total amount of fluoride consumed to the point where they have clinical tooth mottling and laboratory evidence of fluorosis. . . . There are other pathological entities which give rise to polydipsia and polyuria. These would include central diabetes insipidus, pyschogenic water ingestion, renal medullary disease, including hypercalcemic nephropathy, hypokalemic nephropathy and anatomic and vascular disturbances and those diseases causing solute diuresis. Consumption of water in any of these disorders is excessive and could lead to fluoride toxicity in a community with acceptable fluoride concentration. Therefore, a portion of the ingested water that these children consume should be supplied from a nonfluoridated source.”
SOURCE: Greenberg LW, et al. (1974). Nephrogenic diabetes insipidus with fluorosis. Pediatrics. 54(3):320-2.